This study foccuses on accidents associated with ammonia and refrigeration.
Around 8:00 a.m., an operator smelled mercaptans (strong-smelling gas < 1 ppb, toxic in high concentrations) in the zinc dialkyldithiophosphate (ZDDP) unit of a site that manufactures lubricant additives. He collected a sample of mercaptan that had been sitting in the adjustment tank for two days awaiting transfer when the high-temperature alarm went off in the control room. Around 9:00 a.m., analyses confirmed that the mercaptan had thermally decomposed. An inerting test involving the addition of a mixture of zinc oxide and water failed at around 11:00 a.m. because of technical difficulties that delayed preparation of the neutralisation mixture in a mobile mixer (plug/socket connection issues, mixture prepared too quickly). The gas treatment system at the unit overloaded, allowing a strong-smelling cloud of gas to drift off site. At 10:00 a.m., the plant operator implemented the internal emergency plan and informed the regional prefecture at around 11:30 a.m. Thirty-three communities were alerted via various emergency alerts. Neutralization tests conducted in the late evening failed. The wind then shifted, blowing the smell south-east to the Paris area and north-west over the Channel and towards the south of England during the night. Tens of thousands of people were bothered by the unpleasant aroma, with some complaining of nausea, headache and vomiting. Emergency services responded to over 20 calls in the Rouen area. The prefect put together an information team on Tuesday morning and implemented an external emergency plan at 10:35 a.m. From Wednesday morning to Friday evening, a new method made it possible to 'safely' neutralise the 36 tonnes of decomposing mercaptan in batches of 12 tonnes and haul it by lorry to an incineration plant. According to upper bound calculations, the decomposition released 95 kg of hydrogen sulphide, which was eliminated by the treatment system, and 545 kg of mercaptans that were not totally treated (272 kg released into the air). The accident received extensive media attention in France and abroad due to the area covered by the gas cloud. The tank was rinsed and the external emergency plan was ended on 6 February. The operating losses are temporarily estimated at several hundred thousand euros (plant shut down for the duration of the accident, ZDDP shop shut down for three months afterwards).
Multiple causes were identified:
- On Friday 18 January, an operator mistakenly turned on the adjustment tank's mixer instead of the recirculation pump via the unit's control panel. A batch of mercaptan at 94 °C, transferr [...]
During his shift, an employee of a special chemical products plant noticed at 1:20 pm a release of white smoke through the vents on an intermediate storage tank containing acrylic acid (AA, C3H4O2, flammable and corrosive substance, boiling point: 141°C). The tank (70 m³, 75 mm stainless steel shell) had been filled in preparation for a distillation column filling test; moreover, it was heat insulated and inerted with nitrogen. The employee sounded the alarm; a crew of internal fire-fighters attempted to stop the exothermic polymerisation rea [...]
At a Seveso-classified plant producing substances used in medical imaging, a temperature control defect on a biconical dryer caused product decomposition during the drying cycle. The subsequent pressure surge led, around 10 pm, to the explosion of part of the glass piping (a pipe elbow connecting the dryer to its vacuum pump). At the time, the dryer was holding 1,800 kg of a mix containing ethanol and an product releasing iodine (I2), hydrochloric acid (HCl) and nitrogen oxides (NOx) when decomposing. I2 was discharged into the atmosphere via b [...]
An explosion occurred around noon while conducting hot work (with a disc saw) on a 320-m³ fixed-roof tank at a pharmaceutical plant employing 240 personnel. The tank cover was blasted 20 m away and the subcontractor performing cutting works was killed. Three other subcontractors and a plant employee were severely burnt and injured by the shock wave. Notified by neighbours and not by the operator, fire-fighters arrived on the scene 15 min after the explosion and promptly extinguished the fire. Municipal and provincial authorities as well as Reg [...]